Light emitting device

1. A light emitting device, comprising: a substrate; a buffer layer disposed on an r-plane of the substrate, the buffer layer having a rock salt structured nitride; and a light emitting structure disposed on the buffer layer, a primary surface of the light emitting structure being an a-plane.

2. The light emitting device as claimed in claim 1 , wherein the buffer layer has a lattice constant in a range of 4.74 Ř5.52 Å.

3. The light emitting device as claimed in claim 1 , wherein the buffer layer has a lattice constant in a range of 5.11 Ř5.18 Å.

4. The light emitting device as claimed in claim 1 , wherein the buffer layer is formed of at least one of LaN, ThN, PrN, NdN, or SmN.

5. The light emitting device as claimed in claim 1 , further comprising an undoped semiconductor layer disposed on the buffer layer.

6. The light emitting device as claimed in claim 1 , wherein the substrate is formed of at least one of sapphire Al2O3, SiC, Si, GaAs, GaN, ZnO, Si, GaP, InP, Ge, or Ga2O3.

7. The light emitting device as claimed in claim 1 , wherein the light emitting structure includes: a first conduction type semiconductor layer disposed on the buffer layer, an active layer disposed on the first conduction type semiconductor layer, and a second conduction type semiconductor layer disposed on the active layer.

8. The light emitting device as claimed in claim 1 , wherein the light emitting structure includes GaN grown in the a-plane.

9. The light emitting device as claimed in claim 8 , wherein the buffer layer has a crystal plane vertically overlapped with the a-plane of the GaN of the light emitting structure.

10. The light emitting device as claimed in claim 8 , wherein the substrate is a sapphire substrate, and wherein the r-plane of the sapphire substrate, a crystal plane of the buffer layer, and the a-plane of the GaN of the light emitting structure vertically overlap one another.

11. The light emitting device as claimed in claim 8 , wherein the buffer layer includes n (Where, n is 2 or an integer greater than 2) rock salt structured nitride crystal planes, and wherein the light emitting structure includes n a-plane GaN disposed on the n rock salt structured nitride crystal planes.

12. The light emitting device as claimed in claim 11 , wherein each of the n rock salt structured nitride crystal planes of the buffer layer has a size varied with nitrides.

13. The light emitting device as claimed in claim 11 , wherein the n is three.

14. The light emitting device as claimed in claim 13 , wherein the substrate is a sapphire substrate having a crystal cell size of 15.34 Å in an α-axis direction.

15. The light emitting device as claimed in claim 14 , wherein the crystal cell size of the sapphire substrate is 4.75 Å in a β-axis direction.

16. The light emitting device as claimed in claim 15 , wherein the crystal cell size of the a-plane GaN is 5.52 Å in an m-axis direction.

17. A light emitting device, comprising: a substrate; a buffer layer disposed on an r-plane of the substrate, the buffer layer having a nitride; and a light emitting structure disposed on the buffer layer, a primary surface of the light emitting structure being an a-plane, wherein a lattice mismatch ratio of the buffer layer with the light emitting structure of the a-plane is 3% or under in a c-axis direction, and 10% or under in an m-axis direction, and wherein a lattice mismatch ratio of the buffer layer with the substrate of an r-plane is 12% or under in an α-axis direction and 4% or under in a β-axis direction.

18. The light emitting device as claimed in claim 17 , wherein the buffer layer has a lattice constant in a range of 4.74 Ř5.52 Å.

19. The light emitting device as claimed in claim 17 , wherein the buffer layer has a lattice constant in a range of 5.11 Ř5.18 Å.

20. The light emitting device as claimed in claim 17 , wherein the buffer layer is formed of at least one of LaN, ThN, PrN, NdN, or SmN.